Spinal needle



United States Patent Inventor Wesley J. Howe Franklin Lakes, New JerseyAppl. No. 671,635 Filed Sept. 29, 1967 Patented Nov. 17, 1970 AssigneeBecton, Dickinson and Company,

East Rutherford, New Jersey a corporation of New Jersey SPINAL NEEDLE 1Claim, 4 Drawing Figs.

U.S. Cl 128/221', 128/347 Int. Cl A6lm 5/32, A6lb 17/34 Field of Search128/2l4.4,

Primary Examiner-Dalton L. Truluck Attorney-Kane, Dalsimer, Kane,Sullivan and Kurucz I ABSTRACTi A spinal needle having two portions ofdifferent diameter, and which is accurately dimensioned to facilitateentry and positioning in the spinal cord. The needle is hollow and has asharpened point section of reduced diameter connected by a taperingintermediate portion to an enlarged portion which extends to a hubmember. A stylet is also provided which has an external configurationidentical to internal configuration of the hollow needle.

//5 gym/2% SPINAL NEEDLE BACKG ROUND AND SUMMARY OF THE INVENTIONmediately adjacent dura mater, the latter of which is the.

thickest and most substantial of the variouslayers surrounding thespine. The dura and the arachnoid are usually closely adjacent to eachother, and both are penetrated by-the spinal needle as if they were asingle membrane.

In giving spinal injections, the needle and stylet must penetrate thedura and arachnoid, and enter the subarachnoid space which contains thespinal fluid. Usually, the distinct scnsation is imparted to the fingersof the doctor as'the needle penetrates the dura. However, this sensationis not always apparent, especially when a smaller diameter needle isused. Therefore; it has been current practice to interrupt the advancement of theneedle and frequent intervals, to withdraw thestylet,.and observe whether or not fluidappears in the hub of theneedle; the presence of fluid indicating that the needle has entered thesubarachnoid space.

When the fluid indicates that. the needle is properly posi- Y tioned, asyringe containing the selecteddosc of anesthetic or other solution iscarefully attached to thehub. An attempt is then made to aspirate thefluid into the syringe by-drawing on the plunger to once again makecertain that the tip of the needle is still in the subarachnoid space.lffluid-again appears, the injection is made.

The presently used injection proccdures'havemany disadvantages. First,the interruption of the insertion of the needle to check for penetrationof the dura is most uncomfortable to the patient. Also, the resultingtime delay increases the opportunity for a sudden movement by thepatient which may tear the puncture opening or break the needle.

Second, the needle may be advanced. too far through the dura such thatit may strike or even pierce the posteriorsurface. If this occurs, theneedle must be retracted and there exists the possibility that partof-the injection may exit through the perforation.

Third, a small diameter needle may lack the degree of stiffnessnecessary to properly control its direction during insertion and iseasilybroken.

Fourth, the use of a larger diameter needle toirnprove the;

stiffness will result in increased trauma and may cause excess coring ofthe body tissue into the boreof the needle. Also, a larger needle willincrease the sizeof the puncture opening through the. dura which willpermit the loss ofspinal fluid from the subarachnoid space uponwithdrawal of the needle. This loss of fluid is a major cause of-spinalheadache.

In general, the invention relatcsto a spinal needle comprising aninitial portion having a precise outside diameter; a rear portion havinga precise outside diameter somewhat larger than that of theinitialportion, and a-tapered portion joining the initial and rear portions.

lt isan object of the present invention to provide a spinal needle whichmay be advanced to its final position by a con-.

tinuous uninterrupted insertion operation. lt-is-a further object.

to provide a needle which gives a distinct sensation to the doctor whenit enters a proper distance into the subarachnoid space ofthe spinalcolumn.-

lt is another object of this invention to provide a spinal nee dle whichhas a high degree of stiffness and strength, but at the same time may beinserted with a minimum of trauma and coring.

. adjacent the taper 13. It has been found that if the length A isAdditional objects and advantages of the present invention will becomeapparentto one skilled in the art from the following detaileddescription.

BRlEF DESCRIPTION OF THE DRAWINGS FIG. 1 is aside view of the needle andmating stylet'of the present invention;

DESCRIPTION 05 THE PREFERRED EMBODIMENT Referring to the drawings, theneedle of the subjectinvention is generally designated at 10', and itsmating stylet at 20.

The needle 10 includes a forward portion 11, a rear portion l2 ofgreater diameter, and a conical or tapered connectingportion 13. The tipof the needle is'beveled, as at 14, in any con ventional manner. Theneedle is joined to a standard hub 15',

.such as the Luer-Lok hub, which maybe either metallic or plastic. Thehub --is provided with a slot 16- in its outer periphery for the purposehereinafter set forth.

The foru'ardportion H of the needle is of relatively large gage (11s..small diameter) to minimize the incision or puncture. For purposes ofexample, a needle having an outside diameter of approximately ,02 inchesand a bore diameter of .Ol inches (commonly called 25 gage in theindustry) has been found to be very satisfactory.

The rear portion 12 is of relatively small gage to add the requiredstiffness to the structure and eliminate the need for a needle guide orother external means of support against bending during insertion. Forexample. if the rear portion has an outside diameter of approximately.035 inches and a bore diameter ofapproximately .023 inches (20 gage)very satisfactory results are obtained.

It is thus apparent that the needle of the present invention retains theadvantageous features of both the large gage and small gage needle, yetretains none of their disadvantages. The enlarged diameter rear portionhas the effect of adding stiffness to the needle, while the smallerforward portion has the effect of minimizing the incision or puncture.

The transition from the forward to the rear portions is accomplished bya tapered or conical portion 13 which is smoothly blended into theadjacent surfaccsto minimize the resistance to insertion.

Animportant feature of the present invention is the particular length ofthe forward portion 11, designated A in FIG. 4. In use, the forwardportion 11 pierces the dura and enters the subarachnoi'd space ofthe'spine. When the tapered portion 13 reaches the dura, the increasedresistance gives a distinct sensation to the hands of the doctor suchthat he will be aware of the needles exact position. By design, thelength A of the portion 11 is such that the tip of the needle-will beatthe most favorable depth in the subarachnoid space when the dura isseven thirty-seconds of'an inch (or approximately .22 inches) verysatisfactory results are obtained. The particular length'A is alsocritical by reason of the fact that a needle having a forward portionofa length greater than seven thirty-seconds of an inch will tend to bendor break at point l7'during the insertion operation. This dimension mayotherwise vary to a slight extent depending on the age and size of thepatient, as well as the exact portion of the spine to be entered.

The angle of taper B as seen in FIG. 2 should be in the order of 35 foroptimum penetration characteristics. Also. an angle. of this order hasbeen found to be sufficient to give the required distinct sensation tothe hands of the doctor upon reaching the dura.

The overalllength C of the needle varies'considerablyaccording to thespecific use ofthe spinal tap, but typically is in the order of} /2inches.

In the preferred embodiment, the stylet or obdurator 20 includes aforward portion 21 of a diameter closely conforming to the bore diameterof portion ll, a rear portion 22 of a diameter closely conforming to thebore diameter of portion 12, and a conical connecting portion 23. Thetip of the stylet-is beveled at an angle corresponding to the angle at14. The stylet'is joined to'a handle 25 in a conventional manner, thehandle including a key 26 adapted to engage the slot 16 of the hub toeffect alignment of the beveled surfaces l4 and 24 when assembled asshown in FIG. 4.

The stylet could of course be of constant diameter throughout itslength. However, it is preferred to have its external shape closelyconform to the shape of the bore of the needle to provide extra strengthfor the needle. Similarly, the bore of the needle could be of constantdiameter throughout. It is preferred however to utilize a larger borediameter in the rear portion 12 since this improves the flowcharacteristics no sense limited thereby and its scope is to bedetermined byv that of the appended claims.

lclaim:

i. In combination, an accurately dimensioned tubular integral spinalneedle having a distal end portion, an intermediate portion. a proximalend portion and a bore therethrough, a hub mounted on the rear end ofthe proximal end portion, the forward end of the proximal end portionterminating at the rear end of the intermediate portion and the forwardend of the intermediate portion terminating at the rear end of thedistal portion, the forward tip of the distal portion being beveled, thedistal portion having a precisely determined outside diameter in theorder of .02 inches and precisely determined length in the order of .22inches to minimize the size of the puncture made by the needle uponinsertion and to assure that insertion is at the proper depth, theproximal end portion having a precisely determined outside diameter inthe order of .035 inches to provide a needle of desired stiffness. theintermediate portion being tapered and joining the distal and proximalend portions with the angle of taper in the order of 3.5" so as to joinsaid distal and proximal end portions in a smoothly blended manner tominimize resistance to insertion of the needle, the bore ofsaid needlehaving a surface configuration approximating the outer configuration ofsaid needle, a stylet removably inserted in the bore otthe needle andhaving an outer configuration and diameter substantially conforming tothe surface configuration and diameter of the bore of the needle soasito substantially fill the bore ofthe needle when inserted therein.and said stylet having a beveled distal tip which may be aligned withthe beveled distal tip of said needle when said stylet is positionedwithin the bore of said needle to facilitate proper insertion ofsaidcombination.

